This invention relates to bio-compatible and blood-compatible materials and their method of preparation and more particularly to an improved bio-compatible and compliant material of the type described which may be topically or internally applied or contacted by biologicals, blood, or tissue, as, for example, a burn dressing, a surgical dressing, a cardiovascular graft or implant material, and the like, and to the method of making the same.
There are many instances in medicine in which there is a need for a bio- and blood-compatible material for human and animal use and for use in equipment contacted by biologicals or blood, e.g., tubing, containers, valves, etc. For example, in extra-corporeal circulation of blood, i.e., heart or artificial kidney there is a tendency for blood to coagulate on contact with a "foreign surface", see, for example, U.S. Pat. Nos. 3,642,123 and 3,810,781. Also, products such as heart valves, materials used in coronary and vascular grafts, and catheters, oxygenator tubing and connectors tend to cause thrombosis of the blood.
In addition to the above, materials used as burn dressings and surgical dressings should be bio- and blood compatible. In the case of such dressings, an area in which the present invention finds particular utility, there are additional requirements because of the use of the materials.
As is known in the art, and described in U.S. Pat. No. 3,800,792, treatment of second and third degree burns involves a number of phases, including cleaning and stabilizing the wound area to the development of a granulation bed at the wound site. The final phase of treatment is usually the autografting phase which sometimes takes place some period of time after development of the granulation bed. The maintenance of the granulation bed is a necessity until such time as autograft is available and successful autografting is completed.
Several different approaches have been used to preserve the wound site, i.e., granulation bed, for example, application of wet dressings which must be changed frequently and tend to add to patient discomfort. Homografts, heterografts and synthetic dressings have also been used.
Accordingly, a wide variety of dressings, characterized as biological and synthetic, have been used in the treatment of burn wounds. Biological dressings include any dressing that has one or more biological components, i.e., protein, carbohydrates, lipids and the like. Presently, homograft and porcine xenograft skin are dressings currently used to maintain the granulation bed.
In burn patients with large areas of burn tissue, the amount of available skin (autograft) is limited and temporary dressings are required for long periods of time to maintain the granulation bed. Homografts (cadaver skin) is the current dressing of choice, when available. Unfortunately, homograft has a limited shelf life and is relatively expensive, i.e., $85.00 to $90.00 per square foot. Human amniotic membrane has also been used but is less desirable than cadaver skin. Lack of availability and short shelf life are also drawbacks.
Xenograft (porcine) skin is commercially available but is considerably less effective than homografts and autografts. Short shelf life, sterility and limited application are known disadvantages of this material, in addition to an antigenicity problem.